In 40 patients with neoplastic disorders treated with chemotherapy containing anthracyclines or 5-fluorouracil, objective changes of the oral mucosa were registered in 22 patients (55%). Serum IgG and IgA levels and the mean serum IgG/IgA ratio were normal. On the contrary, the mean IgG/IgA salivary ratio was 1.27 (normally below 1.0) due to an increased salivary concentration of IgG (mean 0.095 g/l), but also due to a decreased IgA concentration (mean 0.075 g/l); the IgG/IgA ratio in saliva was higher in patients with objective changes of the oral mucosa (1.53). Values of the periodontal indices were compatible with the diagnosis of a manifest periodontal disease, which tended to be more severe than in control groups. A positive correlation between the gingival index and concentration of IgG in saliva, a non-linear correlation between the gingival index and salivary IgA and a positive linear correlation between serum IgA concentration and intensity of periodontal attachment level recession, indicate local and systemic immune responses to periodontal tissue alterations and dental plaque components. The IgA related local humoral immune response is, however, operating at a lower concentration level than in healthy individuals.